设计一个 StudentInfo 类，它能保存： （1）学生名字； （2）学号，格式为定长的10个字符； （3）专业名； 自行设计相应成员函数。 再设计一个 Grades 类，继承上述类，它能保存：考试成绩，共六个科目。 它有一个成员函数，getAverage，返回六科平均成绩。 自行设计另外的相应成员函数。 编程任务： （1）定义一个 Grades 类的对象数组，长度为 3，用户依次输入学生信息，保存到对象数组当中，最后按平均分数从高到低，依次输出同学的个人信息和平均分。 （2）检测输入有效性，保证输入的成绩是 [0, 100] 的实数。 （3）要求使用多文件结构c

为了实现这个任务，我们需要将类的声明和定义分别写在不同的文件中。下面是实现这个任务的代码示例：

**StudentInfo.h:**

#ifndef STUDENTINFO_H
#define STUDENTINFO_H

#include <string>

class StudentInfo {
public:
    StudentInfo();
    StudentInfo(const std::string& name, const std::string& id, const std::string& major);
    void setName(const std::string& name);
    void setId(const std::string& id);
    void setMajor(const std::string& major);
    std::string getName() const;
    std::string getId() const;
    std::string getMajor() const;
private:
    std::string name;
    std::string id;
    std::string major;
};

#endif // STUDENTINFO_H

**StudentInfo.cpp:**

#include "StudentInfo.h"

StudentInfo::StudentInfo() {}

StudentInfo::StudentInfo(const std::string& name, const std::string& id, const std::string& major)
    : name(name), id(id), major(major) {}

void StudentInfo::setName(const std::string& name) {
    this->name = name;
}

void StudentInfo::setId(const std::string& id) {
    this->id = id;
}

void StudentInfo::setMajor(const std::string& major) {
    this->major = major;
}

std::string StudentInfo::getName() const {
    return name;
}

std::string StudentInfo::getId() const {
    return id;
}

std::string StudentInfo::getMajor() const {
    return major;
}

**Grades.h:**

#ifndef GRADES_H
#define GRADES_H

#include "StudentInfo.h"

class Grades : public StudentInfo {
public:
    Grades();
    Grades(const std::string& name, const std::string& id, const std::string& major,
           double grade1, double grade2, double grade3, double grade4, double grade5, double grade6);
    void setGrades(double grade1, double grade2, double grade3, double grade4, double grade5, double grade6);
    double getAverage() const;
private:
    double grades[6];
};

#endif // GRADES_H

**Grades.cpp:**

#include "Grades.h"

Grades::Grades() {}

Grades::Grades(const std::string& name, const std::string& id, const std::string& major,
               double grade1, double grade2, double grade3, double grade4, double grade5, double grade6)
    : StudentInfo(name, id, major), grades{grade1, grade2, grade3, grade4, grade5, grade6} {}

void Grades::setGrades(double grade1, double grade2, double grade3, double grade4, double grade5, double grade6) {
    grades[0] = grade1;
    grades[1] = grade2;
    grades[2] = grade3;
    grades[3] = grade4;
    grades[4] = grade5;
    grades[5] = grade6;
}

double Grades::getAverage() const {
    double sum = 0;
    for (int i = 0; i < 6; i++) {
        sum += grades[i];
    }
    return sum / 6;
}

**main.cpp:**

#include "Grades.h"
#include <iostream>
#include <algorithm>

int main() {
    Grades students[3];

    for (int i = 0; i < 3; i++) {
        std::string name, id, major;
        double grades[6];

        std::cout << "Please enter student's name: ";
        std::getline(std::cin, name);
        students[i].setName(name);

        std::cout << "Please enter student's ID: ";
        std::getline(std::cin, id);
        students[i].setId(id);

        std::cout << "Please enter student's major: ";
        std::getline(std::cin, major);
        students[i].setMajor(major);

        std::cout << "Please enter the grades for six courses: ";
        std::cin >> grades[0] >> grades[1] >> grades[2] >> grades[3] >> grades[4] >> grades[5];

        // Check input validity
        while (std::cin.fail() || std::any_of(grades, grades + 6, [](double grade){return grade < 0 || grade > 100;})) {
            std::cout << "Invalid input! Please enter the grades again: ";
            std::cin.clear();
            std::cin.ignore(10000, '\n');
            std::cin >> grades[0] >> grades[1] >> grades[2] >> grades[3] >> grades[4] >> grades[5];
        }
        students[i].setGrades(grades[0], grades[1], grades[2], grades[3], grades[4], grades[5]);

        std::cin.ignore(10000, '\n');
    }

    // Sort students by average grades
    std::sort(students, students + 3, [](const Grades& s1, const Grades& s2){return s1.getAverage() > s2.getAverage();});

    // Output students' information
    for (int i = 0; i < 3; i++) {
        std::cout << "Name: " << students[i].getName() << std::endl;
        std::cout << "ID: " << students[i].getId() << std::endl;
        std::cout << "Major: " << students[i].getMajor() << std::endl;
        std::cout << "Average grade: " << students[i].getAverage() << std::endl << std::endl;
    }

    return 0;
}

注意，在编写多文件结构程序时，需要先编译每个文件，然后将它们链接起来。假设我们的文件名是 StudentInfo.cpp、Grades.cpp 和 main.cpp，我们可以使用以下命令编译和链接：

$ g++ -c StudentInfo.cpp
$ g++ -c Grades.cpp
$ g++ -c main.cpp
$ g++ -o program main.o StudentInfo.o Grades.o
$ ./program